The long-term goal of this research program is to understand the immunochemical properties of bacterial poly-N-acetyl glucosamine (PNAG) and utilize this information to produce an effective vaccine for multiple Gram-positive and Gram-negative bacterial pathogens that express PNAG as a surface polysaccharide. PNAG is produced by many clinical isolates of S. epidermidis and almost all strains of S. aureus, the two most common causes of nosocomial bacterial infection, as well as by pathogenic E. coli, Yersinia spp. including Y.pestis, Bordetella spp. and Actinobacillus spp. All of these organisms are significant causes of human and animal disease. Optimal opsonic-killing and protective immunity to Staphylococci is engendered when the normally highly acetylated PNAG molecule (native PNAG, >70% N-acetylated) is deacetylated (dPNAG) such that <20% of the amino groups are acetylated. In this proposal, extension of these findings to pathogenic E. coli and Yersinia spp. will be undertaken, using active and passive vaccination against native PNAG and dPNAG to determine the efficacy of this antigen as a broad-based antibacterial vaccine. Antibody activity will be evaluated by binding assays (ELISA), complement deposition ELISA, opsonic-killing assays, and in vivo protection of infected animals. Further aims are to use synthetic (3-1-6 linked glucosamine oligomers to define the chemical structure of the epitopes that bind to maximally protective antibody and evaluate the binding, opsonic and protective efficacy of antibodies elicited by oligosaccharide-protein conjugate vaccines. Fully human monoclonal antibodies to native PNAG and dPNAG will be investigated for potential as passive prophylactic agents and the activity of these Mabs will be enhanced using ribosome or phage display technology to affinity mature the antibodies in vitro. From a public health viewpoint, active or passive vaccination is the most effective strategy to control infectious diseases, and vaccines containing surface protein-conjugated polysaccharide antigens have been highly effective at reducing infection rates by several bacterial pathogens. Since PNAG is produced by multiple and diverse bacterial pathogens, an effective PNAG vaccine could lead to a significant reduction in the burden of both community acquired and nosocomial disease caused by Staphylococci, E. coli, Yersinia spp. including the cause of plague, and possibly other PNAG-producing organisms.